This invention relates to a solid-state laser device for use in oscillating or amplifying a laser beam by the use of an active laser medium of a slab type, thereafter referred to as a slab-shaped laser medium.
A conventional solid-state laser device of the type described is proposed by Jones, Jr. in U.S. Pat. No. 4,214,216. The proposed device comprises a slab-shaped laser medium having a pair of end surfaces and a pair of principal surfaces contiguous to the end surfaces. The slab-shaped laser medium is interposed between a pair of excitation lamps, namely, flash lamps with spacings left between the principal surfaces and the excitation lamps, respectively. A cooling medium, such as gas, liquid, or the like is caused to flow through the spacings so as to cool the slab-shaped laser medium.
In the above-mentioned laser device, a laser beam travels in a traveling direction from one end surface of the slab-shaped laser medium to the other, by causing total internal reflections to occur on each of the principal surfaces. Thus, the laser beam travels along a zigzag light path which intermittently intersects a center portion of the slab-shaped laser medium. The center portion may attain a high temperature in comparison with the principal surfaces cooled by the cooling medium. As a result, a thermal gradient inevitably occurs in the slab-shaped laser medium.
As mentioned before, the zigzag light path alternatingly passes through a low temperature portion, such as an adjacent portion of each principal surface, and through a high temperature portion, such as the center portion. This serves to make the temperature distribution uniform in the slab-shaped laser medium. Accordingly, the slab-shaped laser medium can produce an output laser beam of high output energy as compared with a laser medium of a rod type.
Recent trends require high optical energy of the output laser beam, as such a laser device pervades a wide variety of technical fields. However, the slab-shaped laser medium has a low conversion efficiency between electric energy used to excite the slab-shaped laser medium and the optical energy of the output laser beam. Thus, a laser device having a high optical output energy becomes large in size.
Under the circumstances, a great deal of input electric energy must be supplied to the solid-state laser device in order to attain an output laser beam of high optical energy.